Nearsightedness can be corrected by using eyeglass lenses that are a. concave in shape and cause light rays entering the eyes to converge. b. convex in shape and cause light rays entering the eyes to converge. c. convex in shape and cause light rays entering the eyes to diverge. d. concave in shape and cause light rays entering the eyes to diverge.

Concave in shape and cause light rays entering the eyes to diverge.

Explanation:

Nearsightedness is also called myopia. It is a defect in the human eye in which a person is able to see nearby objects clearly but the far objects are seen blurry. In this type of defect, the light is unable to focus on the retina as a result far objects appears blurry.

For the correction of this defect a concave lens is used. It helps to cause light entering eyes to diverge. So, the correct option is (d).

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

where is unknown. because the position is parabolic, there is symmetry about the midpoint at , and we know that

so that the position function is

which means the velocity is

then the total distance traveled is

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at and ends at , so its displacement is 0.